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Decoding obd1 check engine light

Demonoid369

Demonoid369

NAXJA Forum User
NAXJA Member
Location
Salem, OR
91' 4.0l xj
So I've gathered that you turn the key on off on off on but the info I'm having trouble gathering is how do you read it? I've read that you just count the flashes and go from there which would mean I have 13 flashes but then again I've read you have to count the pauses between the flashes? Any insight? And once you have the code where do I look to find it what it is
 
The code will flash is patterns. Flash ... Flash... Flash...... Flash...flash...flash...flash...flash...... (35)
Then will repeat. Look at the pauses between flashes. A short pause(...) will indicate it is still relaying the first number of the code. A long pause(.....) indicates it is ready to flash the next number in sequence.
 
You're in Oregon and I just got rid of my Verdict scan-tool or I'd def scan it for ya.
 
https://vimeo.com/169023829
This is the check engine sequence I get, anyone want to break it down for like I'm stupid?(partially true) is the first flash indicating the start of the codes or is it part of a code? Because I'm reading it as either 12 or 24. Just trying to understand how it works.
 
I got code 12, direct battery input to PCM was disconnected within the last 50 key on cycles. (start of test)

Code 41, an open or shorted condition in generator field control circuit.

Code 55, end of test (paraphrased).

Note I've had my codes repeat on occasion, same code twice. Which makes me question the validity o the programming on occasion.
 
12, 41, 55

12 is just the start of code flashing from what I just read, but 8Mud may be right.

the error code is 41

and I will defer to 8Muds statement on code 55 as being the end of the string?

Good evening (here) Mr Mud!!!!
 
Last edited:
That would make sense as I looked up 41 and that is what a alternator would fall under which in this jeep is true as the alternator isn't working
 
So the 12 part. Next time this 91' xj gets the check engine light. Should I just wait till after the 12 goes then count for the engine code or always count that first?
 
Theoretically you should only get a code 12 if the battery has been recently disconnected or maybe a fuse (my code list is for a 95 and the programming may be slightly different). In practice I seem to always get a code 12 at the beginning. And always get a code 55 at the end. Sometimes mine will repeat the code 55 twice.

I've also noticed that the code lists on the internut sometimes have slight differences.

I usually repeat the code retrieval sequence at the least three times.
 
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